Embodiments of the present invention relate to systems and methods and their components for position determination of a movable object, and in particular to a position determination by means of light emitting diodes (LED) and corresponding light sensors.
Light emitting diodes (LEDs) gain ever more popularity. More and more, LEDs also replace conventional illuminants, like for example thermal emitters (light bulbs, etc.) and other illuminants, for example generating lights by exciting gases. LEDs enable a fast data transmission by modulation of the excitation current of the LEDs. Thus, the LEDs are substantially different from the above-mentioned conventional illuminants also with respect to their serviceability and fields of use.
A technology operating in the visible range of light is the so-called “Visual Light Communication” (VLC) which uses light in the visible wavelength range (approximately 400 nm to 800 nm) for an optical data transmission. The VLC technology may further also be used for position finding purposes. Thus, US 2009/0171571 A1 describes a VLC-based navigation system, wherein four VLC transmitters are on the one hand coupled to a corresponding lamp module each in the form of an LED and on the other hand to a navigation server. For location determination, the lamp modules transmit so-called pilot signals which the mobile device receives. The determination of the position of the mobile device is then executed by a triangulation, either by the navigation server or by the mobile terminal device itself. For the transmission of the pilot signals, the VLC-based navigation system uses lamp modules with RGB-LED (Red-Green-Blue), each comprising three light emitting diodes of different colors with the colors red, green and blue and which combine their light so that all in all white light is generated. Here, the different lamp modules generate the white light each by a different combination of red, green and blue light wavelengths and the pilot signals of the different RGB-LEDs are correspondingly transmitted in different wavelengths. The mobile device comprises four photo detectors which receive and evaluate one of those different wavelength ranges each by means of different filters.